


grind the teeth in our empty mouths

by sifu_hotdamn



Series: darling little idiots: a FMAB fusion au [1]
Category: Avatar: The Last Airbender, Fullmetal Alchemist: Brotherhood & Manga
Genre: ATLAverse with alchemy, Alchemy, Alternate Universe - Fusion, Body Horror, Child Abuse, Gen, Implied/Referenced Child Abuse, Ozai (Avatar) Being a Terrible Parent, Ozai (Avatar) is an Asshole, Self-Harm, Zuko and Azula win the Caldera summer reading program, a notable departure from my prior work, there's just some gnarly backstory to get through before then, this is a heavy one please don't let the bits i'm doing in the tags indicate otherwise, unfortunately Caldera City does not have a Pizza Hut, zuko izumi curtis is endgame here
Language: English
Status: Completed
Published: 2021-01-06
Updated: 2021-01-06
Packaged: 2021-03-16 16:02:25
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,532
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28584678
Author URL: https://archiveofourown.org/users/sifu_hotdamn/pseuds/sifu_hotdamn
Summary: Father becomes the Fire Lord.Zuko and Azula start spending most of their free time in the library.A prologue: Zuko and Azula discover alchemy, and attempt a human transmutation.(You don't have to have watched FMAB to understand this, but it will help.)
Relationships: Azula & Zuko (Avatar)
Series: darling little idiots: a FMAB fusion au [1]
Series URL: https://archiveofourown.org/series/2094510
Comments: 16
Kudos: 46





	grind the teeth in our empty mouths

**Author's Note:**

> hello! if you're here because you enjoyed my prior work, this is very much...not that. i've included expanded content warnings for child abuse, body horror, & self-harm in the end notes.  
> take care of yourselves: you can probably skip this installment and infer what happened from the next one!  
> undying gratitude to my brainstorming buddy and sadboy sadbeta (caring), the incandescent [disabledzuko.](https://archiveofourown.org/users/disabledzuko/pseuds/disabledzuko) (sorry for bumming out the communal braincell with this one.) if you need a pick-me-up after reading this, i cannot rec his delightful new [pirate zukka AU](https://archiveofourown.org/works/28538838) highly enough!  
> title is from 'burn' by alkaline trio.

Zuko is eleven years old when his mother disappears.

 _Is she dead?_ he asks his father, sobbing.

 _That, or good as,_ his father snaps back. _Now quit your bawling, stupid boy. You are the Crown Prince now. It would behoove you to learn how to act like it._

Father becomes the Fire Lord. Zuko and Azula start spending most of their free time in the library. At first, Zuko suspects she’s just there to watch for him to slip up, to have some scrap of _typical Zuzu_ to present to Father in exchange for the fleeting warmth of his favor.

(There was little kindness to Ozai before his coronation, but something about the pressure of the new position, or perhaps the absence of his wife, has hardened his last soft edge.

Father never smiles anymore, not even at Azula.)

Eventually - and Zuko’s not entirely sure whether the shift occurs more in her intentions, or in his understanding of them - Azula starts coming to the library for the same reasons as he does.

* * *

While its upkeep varies depending on the literary aptitude of the reigning Fire Lord, the Fire Nation Royal Library has long been considered a jewel of the palace. Azulon may have been cruel, but he was extensively well-read; Father reads little other than military biographies, but does not seem to have paid the library budget enough attention to cut it yet.

Zuko and Azula read through the library, one scroll at a time, sprawled on the soft cushions near the window overlooking their mother’s old garden. Starting that first summer, hot as Father’s temper, they work their way through hundreds of novels, some of them so risqué that Zuko flushes beet-red reading them, and hides them far out of Azula’s reach.

(Azula finds a ladder, and learns a little more than she’d bargained for.)

They start on the piles of histories next. Many are consistent with what they’ve already been taught, but the dustier shelves hold faded tomes, some in languages that the kind, elderly head librarian has to find them dictionaries to understand, that whisper hints of different ways of being, of balance without domination.

(The siblings scoff at these, but they do not forget them.)

* * *

Zuko stumbles upon a new subject to focus on while reshelving scrolls one afternoon.

 _Alchemy,_ the scroll reads, _is an ancient practice, rooted in the use of natural energy to affect matter. The transmutation circles that alchemical practice hinges upon, along with the theory underpinning the three basic steps: comprehension, deconstruction, and reconstruction, were first characterized by Air Nomads._

(Zuko’s never felt like a very strong firebender. Most tutors would describe him as entirely average for his age, and he practices hard enough that his basic katas are sound. Living in the shadow of Azula’s prodigy, however, he’s always been drawn to less arbitrary skills, where diligent work might be more valuable than fortune or birth.

He’s an above-average swordfighter, as his Sifu Piandao used to tell him. Shortly after Ursa disappeared, Father dismissed Piandao, saying a crown prince had more important skills to learn.

Zuko still sneaks into the old practice rooms with his dual dao nearly every night, and practices until his arms get heavy.)

So Zuko begins studying alchemy, or at least what alchemical knowledge has persisted through centuries of it being dismissed as ‘lowbrow cheap tricks’ by Fire Nation nobility, who are coincidentally often firebenders. Azula scoffs, and returns to her firebending scrolls. He uses his first successful transmutation circle to create a small stone turtleduck, and takes to carrying it around in his pocket.

(He rubs its cool, gently textured surface between his fingers whenever Father reprimands him.

It only takes him a few months to wear the pattern on its shell smooth.)

A few of the scrolls mention some great taboo, but do not specify _what_ it might be. It is only the next-to-last scroll Zuko finds that identifies this taboo as something simply described as ‘human transmutation.’ He tries to translate the concept, but using a conversational Air Nomad language dictionary for an ancient, specialized technical document presents challenges.

It takes him a week of referencing other sources to realize that ‘human transmutation’ is taboo because it could hypothetically bring back the dead.

(No one has hugged Zuko since his mother died.

Something inside his chest, all teeth and claws, rages without the anchors of care or touch. At night, he catches himself sobbing as he slashes through practice dummies.)

 _C’mon, ‘zula,_ he begs. _You’re better than me at everything. Help me bring her back._

(Azula does not think she misses her mother. She is repulsed by her brother’s grasping desperation - he’s no fun to tease anymore - and wretchedly longs for any sign of open approval from her father. Maybe bringing Mother back would improve both of their moods.

And, besides, what else is she supposed to do all day?)

They spend nearly a year properly translating texts and compiling notes, and eventually patch together an approximation of a human transmutation circle.

* * *

The day that they decide to attempt it is a stormy one. Azula produces blue fire for the first time in their morning bending lessons.

(Later that day, as he stumbles down to the harbor in a daze, Zuko tries to convince himself that he wasn’t just trying to one-up his baby sister.)

Zuko carefully transcribes the transmutation circle in chalk onto the floor of their mother’s old chambers. Azula tosses a couple freshly strangled pig-chickens into the middle.

(The scrolls discussed the principle of ‘exchange,’ always preceded by a character that they’d never managed to translate.

Years later, Zuko will learn that it meant ‘equivalent,’ and understand why human transmutation is impossible.)

 _No, ‘zula,_ he tells her, as she edges closer curiously. _Stay away from the circle. If something goes wrong, I don’t want it to backfire onto you._

Azula rolls her eyes, but hears the edge of fear in his voice.

She watches from a corner, frozen in terror, as everything falls apart.

* * *

Truth chuckles at him. _You can’t bring back someone who isn’t dead, silly boy, and besides, you haven’t even got the conversions right. Where on earth did you learn how to structure arrays? This whole thing is a mess. I mostly brought you this far out of curiosity._

 _What do you mean, she isn’t dead?_ All the air has been punched out of Zuko’s lungs. _She wouldn’t have left me with him, she wouldn’t -_

_Sorry, kid, but it sure looks like she did. Seems better off now, too. Yikes._

(The furious tears running down his cheeks feel as though they’re coming from someone else.

He pinches himself until he bleeds. The nightmare continues anyways.)

_Unfortunately, now that you’ve peeked at the secrets of the universe, there’s a debt to be paid. Now, I can take that off you or your sister, but one of you has to cover it._

(Zuko returns to the world with a scar across the upper left side of his face that destroys the sight in that eye.)

* * *

Azula’s screaming summons the guards, who take one look at the scene and summon Ozai.

By the time he enters the room, Father is already annoyed - at his disrupted meeting, at having to return to his wife’s old chambers, at the indignant inconvenience of _children -_ and then he takes in the candles, the chalk, the bloody animals, the petrified Azula cradling her brother’s slumped body, and he gets _angry._

 _You stupid children,_ he spits. _What is this peasant witchcraft? Answer me, Zuko!_

Zuko struggles upright, out of his sister’s arms. Ozai sees the scar that now covers nearly a quarter of his face, and his fury ignites.

 _You stupid, worthless boy,_ he hisses. _No true son of mine would enter into spirit-deals like some superstitious old grandmother. Leave this house now, and make sure that I never see what’s left of your face again._

(Zuko packs and leaves in shell-shocked silence, begging his bones to stop trembling.

He doesn’t tell his sister what he discovered. He doesn’t even know where he’d find the words to try.)

Later that night, Azula burns all of their carefully compiled notes in a puff of brilliant blue flame.

* * *

_Fire is the element of power, young Zuko,_ his uncle once told him. _We must always be deliberate in how we wield it._

(No one has seen Iroh since his son’s death at the walls of Ba Sing Se three years ago.)

* * *

What Zuko does not know is that, nearly a millennium ago, Fire Nation alchemists developed a technique to strengthen firebending through alchemy, empowering firebenders nearly as much as the Great Comet. The avatar at the time, an Air Nomad determined to uphold balance, destroyed this knowledge, deeming both the cost and the danger of the method too great for it to persist in the world.

(For centuries, an owl spirit ferociously guarded the last scroll known to document this practice deep in the heart of the Si Wong Desert, until an ambitious junior officer in the Fire Navy absconded with it.

The summer after Zuko turns thirteen, Zhao, now the commander of Ozai’s secret alchemical research division, finally finishes decrypting it.)

**Author's Note:**

> DETAILED CONTENT WARNINGS: Ozai verbally abuses and neglects his children throughout, and eventually banishes Zuko. Zuko experiences his ongoing trauma very viscerally, so language evocative of body horror is used throughout. The self-harm is brief: Zuko pinches himself until he bleeds during his conversation with Truth. You can skip the section that starts "Truth chuckles at him" to avoid it.  
> let me know what y'all think in the comments, or come yell at me [on tumblr](https://sifu-hotdamn.tumblr.com/)


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